Current Storage Area Networks (“SAN”s) are designed to carry block storage traffic over predominantly Fibre Channel standard medium and protocols using fabric networks comprising local area networks (“LAN”s). Expansion of SAN fabric networks is limited in that conventional SAN fabric channels cannot be implemented over geographically distant locations. Conventional Fibre Channel architecture is not suitable for wide area network (“WAN”)/LAN applications. While SCSI and Ethernet may be used to implement a WAN/LAN, these two protocols are not efficient for storage applications. Accordingly, current SAN fabric networks are limited to a single geographic location.
There exist several proposals for moving block storage traffic over SANs built on other networking medium and protocol technologies such as Gigabit Ethernet, ATM/SONET, Infiniband, and the like. Presently, to bridge or interconnect storage data traffic from SANs using one medium/protocol type to another SAN using an incompatible protocol/medium type requires devices and software that perform the necessary protocol/medium translations. These translation devices, hereinafter referred to as “translation bridges,” make the necessary translations between incompatible protocol/mediums in order to serve the host computers/servers and storage target devices (the “clients”). Interconnecting heterogeneous SANs that may be easily scaled upward using these translation bridges is very difficult because the translation bridges usually become the bottleneck in speed of data transfer when the clients (servers and/or storage devices) become larger in number. In addition, in a mixed protocol environment and when the number of different protocols increase, the complexity of the software installed on the translation bridges increases, which further impacts performance.
A limitation of the size of SAN fabric networks, in terms of storage capacity, is cost and manpower. In order to expand the storage capacity of a SAN fabric network, storage devices such as disk drives, controllers, fiber channel switches and hubs, and other hardware must be purchased, interconnected and made functionally operable together. Another major, if not primary, expense is the cost of managing a SAN. SAN management requires a lot of manpower for maintenance and planning. For example, as storage capacity grows, issues such as determining server access to storage devices, backup strategy, data replication, data recovery, and other considerations become more complex.
It is desirable that next generation storage network switch systems will have ingress and egress ports that support different protocols and network media so that different types of host computer/servers and storage target devices may be attached directly to the switch system and start communicating with each other without translation overhead. In order to communicate between any two ports, the source and destination ports must be identifiable in both the source and destination protocol. For example, to send a message or frame from a Fibre Channel port to a Gigabit Ethernet port, the destination port needs to appear as a Fibre Channel port to the connected Fibre Channel source, and the source port needs to appear as a Gigabit Ethernet port to the destination port.
SAN and networking products are usually used in mission critical applications and housed in chassis or racks. When a customer wants to expand this system, one or more chassis are added into the existing domain. However, the user has to power down the existing system and reconnect the new chassis into the existing system. Once the new configuration or topology is complete, the user will have to power on the new system. Unfortunately, this upgrade causes system downtime and potential loss of revenue.
Switches have a limited resource—the switch fabric or routing core. A non-blocking switch must have enough bandwidth to receive traffic at full speed from all ingress ports and direct the traffic to the egress ports without dropping traffic, assuming that the traffic is spread equally across all egress ports and does not congest one of them. Therefore, if all ports connected to the switch have the same data rate, then the switch fabric must have bandwidth greater than the number of ports multiplied by the port speed if it wants to be a non-blocking switch that does not drop traffic.
The problem with existing switches is that the internal switch fabric is fixed in size. If large scalability is desired one has to pay for a large switch fabric that initially is not needed. In present systems a smaller switch has to be replaced when more capacity is needed by a larger switch. This is a disruptive upgrade that causes all nodes connected to the switch to lose connectivity while the upgrade is occurring. In another scenario, multiple smaller switches can be interconnected using lower bandwidth interconnects. However, these interconnects can become congested and limit the throughput of the network.
The majority of the SAN switches are not expandable and typically have a limited number of ports, for example, 16 ports. When a customer needs more than 16 ports, two or more of the 16 port switches must be connected together. Unfortunately, to achieve a non-blocking switch in a typical configuration half of the ports on the switch are then used for interconnect purposes. As every switch system is internally limited to a specific amount of devices that can be coupled with each switch such an interconnection is not desirable. Expansion of an internally fully expanded system can be further achieved through special designed trunk couplings. These couplings are, however, limited in their flexibility as their assignment to the plurality of channels of each switch is static and, thus, not very flexible. It is, therefore, highly likely that traffic within the switch system will be blocked due to an already in-use trunk coupling.
Thus, there is a demand for a more user friendly system reducing the downtime and overall cost of a network switch fabric system.